Portola, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

110
FXUS65 KREV 182135
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
135 PM PST Thu Dec 18 2025

.KEY MESSAGES...

* Mild weather with gusty winds continue into Friday. Localized fire
  weather concerns possible in areas of receptive fuels.

* Wet and windy pattern commences this weekend, lasting into much of
  next week. Expect impacts to holiday travel.

* Good potential for heavy rain Sunday with rises on creeks and
  rivers, with a non-zero risk of heavy mountain snow Christmas Eve
  and Christmas Day.

&&

.DISCUSSION...

Very active weather is expected this weekend through the Christmas
holiday as a progression of atmospheric river storms move through
late weekend into early next week. Storms this weekend will be
characterized as wet, high snow level storms producing moderate to
heavy rainfall with the potential for notable rises on small creeks
and streams along with impacts for urban and poor drainage areas.
See Hydrology section below for more details.

An initial wave of moisture will push through Friday morning through
Saturday morning with 70% rain chances along the Sierra roughly
north of US-50. This could yield rainfall amounts of 0.50-1.00"+
along the eastern Sierra while snow levels hover near 8500 feet.
Western Nevada will see limited spillover with accumulations up to a
few hundredths of an inch.

The main issue for W.Nevada will be wind Friday and potentially
again on Sunday. A potent 700mb jet (around 60kts) could yield
afternoon gusts of around 50 mph along the eastern Sierra and Sierra
Front with wind prone locations exceeding 60 mph. Localized fire
weather concerns due to gusty winds and dry conditions are still
present across portions of the southern Sierra Front into Mono
County as these areas have not seen recent wetting rains.

Sunday and Monday feature a wetter AR storm which could yield
another round of strong and gusty winds ahead of the moisture push
on Sunday. Snow levels look quite high during this event, above 8500-
9000 feet, which would limit snow impacts to the highest peaks.
Otherwise expect periods of heavy rainfall. Median rainfall amounts
over a 48 hour period suggest rain amounts of around 2-4 inches from
the Tahoe Basin into NE California with lesser amounts to the south,
1-1.5 inches across Mono County. W.Nevada could also see upwards of
1 inch of rainfall during this time.

After a brief lull on Tuesday, another potent storm system could
impact the Sierra and western Nevada Christmas Eve and Christmas
Day. This storm could strike a balance of ample moisture with lower
snow levels which could produce snow impacts to the Sierra with snow
lines dipping as low as lake level. Still a lot of details to work
on with this storm but keep a close eye on the forecast if you have
any holiday travel planned. Factoring in wind, snow, and rain
potentials - Saturday and Tuesday probably have the best travel
conditions. Fuentes

&&

.AVIATION...

* Wind impacts will continue as ridgetop winds (FL100) increase to
  50-60kts this evening and continue through Friday afternoon.
  Expect mountain wave turbulence and LLWS for all airfields in the
  Sierra and far W Nevada including RNO. Surface gusts at Sierra and
  W.Nevada terminals could reach 40-45 knots Friday afternoon.

* A short lived wave of precip is also likely to affect flying
  conditions on Friday during the day. Mainly in the mountain areas
  from SVE to TRK/TVL with periods of MVFR-IFR in rain.

* A strong, atmospheric river storm could provide another round of
  strong and gusty winds on Sunday followed by period of heavy rain
  for Sierra and W.Nevada terminals. Snow impacts will be limited to
  the highest Sierra peaks as snow levels remain high at around 8500-
  9000 feet. Chris/Fuentes

&&

.HYDROLOGY...

* Moderate to heavy rains will lead to significant rises on
  rivers and streams Sunday into Monday most notably from the
  Tahoe Basin north through Lassen County, but no mainstem river
  flooding is currently expected. Minor flooding of urban and poor
  drainage areas and rockfall are possible during any prolonged
  periods of high intensity rainfall. Watch for additional rises
  near Christmas Eve and possible flooding concerns especially in
  drainages with large mountain drainages below about 6,000 feet,
  like the Susan River for example.

* You can find river forecasts updated twice daily at: www.cnrfc.noaa.gov

&&


.REV Watches/Warnings/Advisories...
NV...Wind Advisory from 4 AM Friday to 4 AM PST Saturday NVZ002-003-
     005.

     Lake Wind Advisory until 4 AM PST Friday NVZ002.

     Lake Wind Advisory from 4 AM Friday to 4 AM PST Saturday NVZ004.

CA...Wind Advisory from 4 AM Friday to 4 AM PST Saturday CAZ070>072.

     Lake Wind Advisory until 4 AM PST Friday CAZ072.

&&

$$